BLDC motors which are also known as electronically commutated motors have electronic commutation systems rather than mechanical commutators and brushes. BLDC motors are widely used in modern electronic devices due to their several advantages over brushed DC motors, such as more torque per unit of weight, higher efficiency, higher reliability, reduced noise, longer lifetime, elimination of sparks from the commutator, and a reduction in electromagnetic interference.
Conventional BLDC motors are usually three-phase BLDC motors as conventional three-phase BLDC motors have a higher efficiency compared to conventional two-phase BLDC motors. However, three-phase BLDC motors have complicated windings and driving circuits and therefore have higher cost.
European Patent No. 2028747 discloses a two-phase BLDC motor which uses concentrated windings and a two-phase driving circuit with a phase difference of 180 electrical degrees. However, in half of each period, the currents of portions of two coils of the windings in the same slot between adjacent poles have opposite directions and therefore these portions do not generate torque. Thus, this kind of two-phase BLDC motor has a low efficiency.